R.F. choke for CATV system

Abstract

A radio frequency choke for a cable or CATV system is designed for blocking signals from 5 to 1000 MHz and passing 60 Hz AC power. The RF choke has a wire coil that is wound upon a coil form of a predetermined cross section, the coil being formed of a number of successive spaced windings on the form, with each winding being joined to the next by an air coil of at least one turn, formed off the loop. The various successive windings should have different numbers of turns. Forming the air coils tends to tighten the windings onto the form, so that a fixative coating or adhesive can be eliminated or omitted.

What is claimed is: 
     
       1. An RF choke that comprises a coil form of a predetermined cross section, a wire coil wound upon said coil form, said coil including a first lead, a second lead, at least two successive windings in series with one another and disposed in series between said first and second leads, each of said windings being wound upon said coil form with a spacing between a last turn of one winding and a first turn of a next adjacent winding, and a loop formed off the coil form connected in series between said two windings to join said last turn of the one winding and said first turn of the next winding. 
     
     
       2. An RF choke according to claim 1 further comprising a resistor connected in parallel with one of said windings. 
     
     
       3. An RF choke according to claim 1 wherein said windings are each formed of respective different numbers of turns. 
     
     
       4. An RF choke according to claim 1 wherein said coil form includes a core of ferromagnetic material. 
     
     
       5. An RF choke according to claim 4 wherein said ferromagnetic material includes iron powder. 
     
     
       6. An RF choke according to claim 1 wherein said at least two successive windings are wound in the same helical direction. 
     
     
       7. An RF choke that comprises a coil form of a predetermined cross section; a wire coil wound upon the coil form, said coil including a first lead, a first winding of N 1  turns, said first lead being connected to an input side of the first winding, a second winding of N 2  turns, a third winding of N 3  turns, a second lead connected to an output side of said third winding, said first, second and third windings being wound upon said coil form, a first supplementary coil being formed of at least one turn formed off said coil form joining the first and second windings to leave a space on the coil form therebetween, and a second supplementary coil of at least one turn formed off said coil form joining the second and third windings to leave a space on the coil form therebetween. 
     
     
       8. The RF choke of claim 7 wherein said first and second supplementary coils each form a loop that does not contain the coil form. 
     
     
       9. The RF choke of claim 7 wherein said first, second, and third windings all have different numbers of turns. 
     
     
       10. The RF choke of claim 9, wherein N 1  =5 turns, N 2  =7 turns, and N 3  =4 turns. 
     
     
       11. The RF choke of claim 7 wherein said coil form includes a ferromagnetic core. 
     
     
       12. The RF choke of claim 7 further comprising a resistor connected in parallel with said third winding. 
     
     
       13. The RF choke of claim 12 wherein said resistor is on the order of 750 ohms. 
     
     
       14. The RF choke of claim 7 wherein said coil includes at least a fourth winding on said coil form in series with said first, second, and third windings and between said third winding and said second lead. 
     
     
       15. The RF choke of claim 7 wherein said coil form includes a powdered iron core. 
     
     
       16. An RF choke that comprises a helically wound wire coil including a first lead, a second lad, at least two windings in series with one another and disposed between said first and second leads, each of said windings being wound in a common helix but with a spacing between a last turn of one winding and a first turn of a next adjacent winding, which first turn is the next turn in succession in said common helix, and a loop formed off said helix joining said last turn of said one winding and said first turn of the next winding. 
     
     
       17. An RF choke that comprises at least first and second wire coils wound on a common core with a last turn of the first coil being spaced from a first turn of the second coil, and an inductor formed of a wire loop off said core disposed in series between the first and second coils and joining the last turn of the first coil to the first turn of the second coil. 
     
     
       18. The RF choke of claim 17 that also comprises a third wire coil wound on the common core and another inductor formed of a wire loop off said core joining a last turn of the second wire coil with a first turn of the third coil. 
     
     
       19. The RF choke of claim 17 wherein said wire loop is disposed adjacent a space formed between the last turn of the first coil and the first turn of the second coil and at an axial position of said space.